Document Type: SI: Membr.Rev.2021
National Research Council of Italy - Institute on Membrane Technology, CNR-ITM
In this work, the main aspects regarding the permeation of mixtures containing CO2 and permanent gases such as H2 , N2 and CH4 through zeolite membranes have been investigated, focusing on the description of the mass transport mechanisms taking place inside the pores. First, a brief overview about the performance of the main zeolite membranes used in gas separation (e.g. DDR, CHA, AEI, FAU, etc.) was provided, which was expressed in terms of permeability and selectivity of CO2 /CH4 , CO2 /H2 and CO2 /H2 mixtures. The core of this work is an overview of the mass transport through the zeolite pores, with particular attention to the last achievement given by the modelling approach. Moreover, the permeation of binary mixtures has been analyzed; specifically, the effect of temperature, feed pressure and mixture composition on permeance and selectivity has been investigated. The increment of temperature and feed pressure negatively affects the separation performance of zeolite membranes, reducing both CO2 permeance and selectivity. Moreover, the increment of CO2 permeance observed in mixture, paired to the reduction of that of H2 , N2 and CH4 , provides an important improvement in membrane selectivity (e.g., 6 times for CO2 /H2 in SAPO34). Thus, the knowledge of the appropriate operating conditions to be set, associated to the improvements in membrane reproducibility and fabrication cost, will allow to extend the applications of zeolite membranes on industrial scale.